1. Field of the Invention
The invention relates to multi-pole electric circuit breaker systems.
2. Description of the Prior Art
Electric circuit breakers have tripping means which cause tripping of the breaker for interruption of a circuit when a current flows through the breaker which is in excess of a predetermined threshold current. Such a threshold current may, for example, be between three and five times the rated normal operating current for the breaker. Sometimes, the requirement exists that the breaker will trip rapidly when the excess current conditions occur, for example within 0.2 seconds, but requirements sometimes exist for the breaker to withstand overload current for a longer time before tripping. The provision of given tripping characteristics requires careful design of the tripping means in the breaker and, particularly in space-saving designs, it is difficult to provide means for causing common tripping of all breakers of a group, when one of the breakers in the group is tripped.
One method of effecting common tripping is employed in the circuit breaker system described in U.S. Pat. No. 3,550,047 issued Dec. 22, 1970 to Francis L. Gelzheiser and assigned to the assignee of the present invention. A common trip member is rotatably mounted within the circuit breaker enclosure and includes slots at each end. A flat connecting member is keyed into the slots of the trip members of adjacent breakers to provide pivotal movement of the assembly along a common axis. It is desirable to provide an improved circuit breaker system which exhibits ease of assembly and a low degree of lost motion.